Devices and techniques for evaporative cooling are extensively described in the art. Specifically, in the U.S. Pat. No. B1 4,042,010, a method and apparatus are described for humidifying air by injecting a fog with devices driven by pressurized air and water. One of the benefits described is a cooling effect when the fog generated by the device evaporates. In U.S. Pat. No. 4,546,375, a device for the injection of fog into a chamber is described using pressurized air and water in order to humidify an environment such as a building.
Gas turbine engines operate on natural gas or oil to compress incoming air and discharge a highly heated expanded air flow to provide power for an airplane or other transportation and are also commonly used to generate electrical power. There are many installations where gas turbine engines are used to produce electrical power in so-called "co-gen" applications. Typically, these involve a large plant which has a need to supply its own steam and electrical power and employs its own gas turbine to do so. Electric utilities frequently employ gas turbines to provide peak power generating capability that can be brought on line in a rapid manner.
The ability of a gas turbine/electric generator to provide electric power is affected by the temperature of the air entering the gas turbine. Typically, the cooler the inlet air temperature the greater power that can be obtained from the turbine. In many co-gen turbine installations an optimum operating temperature is established where the power produced tends to vary both above and below the optimum temperature. For example, in one gas turbine maximum output power occurs with the inlet air at 48 degrees F. At lower or higher air ambient temperatures the engine must be throttled back to stay within allowable compressor discharge and temperature limits unless the inlet air is chilled or heated to operate at a constant 48.degree. F. See for instance an article by V. De Biasi entitled "New Performance Guarantees for LM6000 Production Gas Turbines", published in Gas Turbine World's January-February 1993 issue.
One technique for controlling the gas turbine inlet air temperature on warm days involves the placement of an evaporative cooling wet media in the path of the incoming air. A wet media, however, introduces an inlet air pressure drop which tends to reduce turbine performance. A wet media also cannot be controlled so that on higher humidity days, when less water is needed to achieve maximum evaporative cooling, an excessive amount of water is still consumed to wet the media. A wet media tends to use a substantial amount of water that is expensive in situations where deionized water is used to protect the gas turbine and is wasteful in areas where water is scarce.
A need, therefore, exists for an evaporative cooling technique which overcomes the deficiencies of wet media and yet is capable of providing a reliable and effective cooling of the inlet air for gas turbines.